This study is concerned with the development of children's imitative behavior in the natural environment. Data were obtained on 24 children over a nine-month period during the second and third years of life. Sources of data consisted of descriptive acounts of imitation by mothers trained in observational recording. Although most of the incidents of imitation consisted of immediate repetitions of the behavior of models, incidents of delayed imitation increased from late infancy to early toddlerhood. Several developmental changes in the content of children's imitations also occurred during this period. The imitation of positive affect and of nonfunctional behaviors decreased as children grew older. Increases with age were found for caretaking, self-care and household chore behaviors, social interaction skills, mannerisms and expressive characteristics of models, and verbal behaviors. The overall pattern of findings suggests that imitation is an important process in the early acquisition of competent behaviour patterns and that the imitation of instrumental and functional behavior patterns increases with age.